Audio content such as music or sound tracks of a movie are usually produced with the assumption of a certain playback level (e.g., the “overall gain” that should be applied to the audio signal during playback, between its initial or decoded form to when it is converted into sound by a speaker, in order to obtain a sound pressure level at the listener's position that is the same as what was intended by the producer of the audio content.). If a different playback level is used, the content not only sounds louder or softer but it may also appear to have a different tonal characteristic. An effect known from psychoacoustics is the nonlinear increase of loudness perception at low frequencies as a function of playback level. This effect can be quantified by equal, perceived loudness contours and by measurements of perceived loudness as a function of playback level and signal characteristics. Commonly, a partial loss of low frequency components compared to other frequencies is reported when the content is played back at a lower level than intended by the producer. In the past, loudness equalization was performed by an adaptive filter that amplifies the low frequency range depending on the playback volume setting. Many older audio receivers have a “Loudness” button that works in that way.